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Hi i have a 97 chevy vortec 5.7 with 312,465 and i recently did a compression test and the compression was way down on cylinder #8 i think im losing coolent into cylinder #8 but it doesnt smoke so is that possible i put new plugs wires cap and rotor and #8 not firing thanks

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How have you determined that #8 is not firing? Normally if you have a coolant leak into a cylinder the spart plug from that cylinder will have white deposits from the burned anitfreeze. Check to make sure that you have spark on that cylinder. If not, the new wires or cap you installed might have a problem or not be seated fully.

Posted on Dec 02, 2014

  • Josh j Dec 02, 2014

    All my plugs are white and just put them in about 3000 miles ago

  • Josh j Dec 02, 2014

    I did a compression test compression ok on all cylinders but #8 it was way down



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SOURCE: 97 chevy vortec 5.7. Can someone tell me why #8

When you say the #8 plug is black it tells me that you may have a broken piston ring that damaged the #8 cylinder wall to the point where oil is coming up and fouling the plug, along with NO compression, or you may have bad valve seals or a bent valve. A compression test would be the best way to go now, and testers are not expensive, you can go to an auto parts store where they will rent you a compression tester. I am only guessing, and you may have to go into the engine, with a possible rebuild or replacement forthcoming. GOOD LUCK FRIEND.

Posted on Nov 28, 2014

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97 chevy vortec 5.7. Can someone tell me why #8 cylinders not firing i changed cap rotor and even switched plug wires thinkin it was the wires no change plug is black all the rest are white doesnt smoke...

If the end of the sparkplug is back, indicates carbon build up. Buy a compression tester, way cheaper and easier, although I'm not sure if it is a head gasket. What color is the smoke that comes out of the tailpipe, a greyish blueish or is it black? Does the engine shudder? Where the spark plugs themselves changed and gapped correctly? It may be detonation also.

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My 97 Chevy 5.7 vortec is missing on cylinders 3, 4, and 5, changed distributor cap and truck ran great for about two hours. Changed fuel filter and there was no change. New plugs and wires summer of 2012....

Well its not exactly ignition or fuel injectors, since cylinder 6 in in the firing order. 1-8-4-3-6-5-7-2
Could be something with the intake again, or the pickup in the distributor. I suppose if you have the multi-port injection inside the plenium it could be some of the spider valves or lines.
You would need to know if those cylinders are firing, and if they have normal compression.

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I think my timing chain jumped time my truck died going down the road kinda like it bogged down then just stopped running and it wont start back when u try to start it it will turn over for couple seconds...

well first off you need to start by checking the compression on all 8 cylinders!!!! to rule out internal engine failure as oppose to jumped timing. its very rare that timing chains will jump especially a double roller chain. get a compression gauge take the plugs out and get a reading on all the cylinders. you should be no more then 10-20psi difference from cylinder to cylinder. but on the chevy motors if there is a problem they usually show well on a compression test! good luck post back up the results then we can go from there.

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Number 1 Cylinder loses Compression

That means u have to replace the piston ring on that piston in the #1 cylinder or check the intake/exhaust valve, it might have problem in sealing the cylinder during compression! If you have done the compression test, those are the main problem of loose compression. The only way to check it is to remove the cylinder head.
Hope that might helps u out!

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I have a 99 chevy c1500 5.7 vortec. 154,xxx has a random misfire on cylinder 6. Losing coolant somewhere, thinking internally. Also has a lifter that will tap for 30-60 seconds randomly when started...

A good test would be a smoke test to see if smoke comes out the intake, another way is to spray carb cleaner on intake port for take cylinder and see if it runs richer. i think you may have a bad intake or gasket these are kown for intake leaks, if you had a bad head it would run hot,i would pull the intake and check the gasket.make sure to use the old design not the new plastic type gasket with rubber oring seals.

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Any engine that has low compression indicates worn internal parts. $$$$ The usual suspects are worn piston rings. Have you checked all 8 cylinders? If so, are they all losing compression, or just certain cylinders? If you have access to a garage, do a compression check on all 8, you may also want to get a cylinder leakdown test, again, on all 8 cylinders. You can then decide what course of action would be best. Good Luch!

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Do a compression test...may be a valve issue.
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I have a 96 chevy blazer with a 4.3 vortec rough

Do a compression test on all of your cylinders when it is cold. Backfiring is a sign of a worn valve seat allowing mixed fuel and air (lit by spark) to be forced back into the intake. You will probably see compression loss on one or more cylinders.

Also... there is a chance that the EGR valve is not totally seated when the engine is cold with just a small blow by. The EGR valve seats coke up over time with black gunk.

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